Evidence obtained this year indicates that dietary arachidonic acid affects cholesterol metabolism and/or transport in guinea pigs. We are planning to conduct a more detailed study of this phenomenon. Plasma lipoproteins. We are planning to a) further characterize the lipoprotein classes in respect to their morphology and peptide composition, b) study whether or not the protein portion of the abnormal lipoproteins found in the C-fed gp is made de novo and c) to study the time course of the appearance of the abnormal lipoprotein species in order to assess their contribution to the spurring of RBC. Studies (b) and (c) will utilize the anti-lipoprotein antibodies prepared this year. Limitation of the intestinal absorption of cholesterol is one mechanism by which certain animal species prevent its pathologcal accumulation. We are initiating a study of the absorption of cholesterol in normal and in cholesterol-fed guinea pigs. The results of these studies together with the information we have obtained earlier on cholesterol catabolism and turnover should enable us to decide which of the mechanism(s) available to limit cholesterol accumulation is not adequate to prevent cholesterol accumulation and the subsequent pathological effects in the guinea pig.